1. Field of the Invention
The present invention relates to a circuit arrangement for arithmetic combination of an analog signal, especially a voltage signal, with a digital value, as well as a method and a circuit arrangement for determining an angle from respective analog signals proportional to the sine and cosine of the angle.
2. Prior Art
Numerous technical applications require the multiplication of an analog signal with a value present in digital form for further processing.
For example, in one application, two analog electrical parameters, which correspond to the sine and cosine of an angle, are used to determine an angle. This sort of problem occurs, for example, in radar engineering, interferometry or laser distance measurement. Also angle sensors, which measure the angle between the direction of a magnetic field and a sensor, for example by means of Hall effect or an anisotropic magneto-resistive effect, supply these type of signals. The determination of the angle from the corresponding analog sine or cosine values requires a multiplication with values, which are appropriately stored first in digital form, in the case of certain computational algorithms. Usually the digital signal or value would be converted to an analog value for performing this kind of multiplication, but that increases the circuitry expenses.
Circuits known for evaluation of measured values from Hall effect sensors or AMR sensors are known from German Patent Document DE-OS 195 43 562. For example, this published patent document suggests determination of an angle by evaluation of the sine and cosine values measured by means of two Hall sensors arranged displaced with respect to each other by means of a circuit device embodying the arctan function. The circuit device embodying the arctan function is comparatively expensive, since for example table interpolating methods or CORDIC algorithms must be consulted.